The Royals left-hander's good start to this season -- 10 starts, 2.69 ERA -- and his anointed status as one of the organization's top young arms makes this a given.

To everyone except Duffy, that is.

"I never feel like I have a set spot on this roster," Duffy said. "I go out there and pitch in every game like it could be my last one with my boys. As cliché as it may sound, it's real."

This attitude spurns from Duffy's tumultuous first four seasons with the club.

Duffy's much anticipated Major League debut in 2011 started inauspiciously as he posted a 5.64 ERA and concerns about his control proved prescient (51 walks in 105 1/3 innings).

The following season went even worse as much of it was lost to Tommy John surgery.

One of the biggest blows came this March, when Duffy, now a four-year veteran, did not make the team out of Spring Training. When he received an early-April callup, Duffy was relegated to bullpen duties.

"Once you start getting comfortable in the big leagues with your position, that's when things start getting taken away from you," Duffy said. "I try to go out there with the mindset that I need to do my job, and that you have to, you can't just coast through anything."

Duffy won't take his spot for granted, but the improvements he's made this season are staggering.

Duffy possesses a sizzling four-seam fastball that averages just below 95 mph with enough running action to make hitters uncomfortable in the box. It's a pitch he's thrown more than 73 percent of the time to left-handers and caused them absolute fits because of it.

The only positive results for lefties from the 131 four-seam fastballs Duffy's thrown to them this season is one single and one walk, according to Brooksbaseball.net. They possess a .035 batting average and a .035 slugging percentage against the pitch.

"I'm just not trying to do too much with it," Duffy said. "In the past, I've tried to just throw it as hard as I can. And now I know that if I just let it go and get down through it, and not necessarily run it up there harder, it'll be commanded better."

Duffy's picked up almost no speed on his fastball (particularly over the last three years), but suddenly he's become remarkably lethal with the pitch.

Take a look at how his four-seamer has evolved in four years (statistics from Brooksbaseball.net):

"I know I'll be hearing pitch efficiency questions for the rest of my life, but at some point hopefully I'll get past that stigma, and I feel like I'm doing a pretty good job of it now," Duffy said.

The numbers all reveal Duffy's transformation this season, but he also concedes that an extra year of maturity has contributed to his ascension.

"When I was younger, even before surgery, I definitely went out there and acted like a kid at times, and I was a kid," he said. "It takes a lot to grow up in this game and it takes a special person to come up here right off the bat and be able to handle everything that's being thrown at you."

Duffy offers one of the most gregarious locker room presences on the team, whether it's coming over to hug Bruce Chen, who just returned from an extended disabled list stint, or joking with outfielder Jarrod Dyson or simply venting his disinterest in soccer as a Ecuador-France World Cup game plays in the background of the locker room.

These are the moments Duffy cherishes, and the reason why he refuses to take a day in the big leagues for granted.

"I've been lucky enough to be given a chance to grow a little bit as a man and I'm very grateful to the Royals for allowing me that time to man up," Duffy said.

Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.